Olefins are known to react with butadiene or other dienes in the presence of rhodium complexes. These reactions are described, for example, in the following prior art documents: U.S. Pat. Nos. 3,013,066 and 3,636,122, which describe the use of a rhodium (I) complex with a cyclopentadiene ligand.
U.S. Pat. No. 3,640,898 describes the use of rhodium complexes comprising a rhodium salt or dimer and an amide or oxide of a phosphine amide.
U.S. Pat. No. 3,502,738 describes the use of dimeric rhodium complexes wherein the counter-ion is an alkali salt, a hydrogen atom H.sup.+ or a nonsubstituted ammonium ion NH.sub.4.sup.+. Also, international patent application WO-A-91/11428 describes the use of a series of rhodium complexes or rhodium salts in the addition of ethylene to linoleic esters or linoleic esters containing conjugated ethylene bonds.
When the diene employed possesses poorly accessible double bonds, the reaction is very slow, as evidenced by the 24 hour period required to effect reaction between ethylene and linoleic esters in patent document WO-A-91/11428. It therefore appears that the economic addition of ethylene to a fatty diene derivative poses difficulties.